From: Jonathan Cameron <Jonathan.Cameron@Huawei•com>
To: Wei Huang <wei.huang2@amd•com>
Cc: <linux-pci@vger•kernel.org>, <linux-kernel@vger•kernel.org>,
<linux-doc@vger•kernel.org>, <netdev@vger•kernel.org>,
<bhelgaas@google•com>, <corbet@lwn•net>, <davem@davemloft•net>,
<edumazet@google•com>, <kuba@kernel•org>, <pabeni@redhat•com>,
<alex.williamson@redhat•com>, <gospo@broadcom•com>,
<michael.chan@broadcom•com>, <ajit.khaparde@broadcom•com>,
<somnath.kotur@broadcom•com>, <andrew.gospodarek@broadcom•com>,
<manoj.panicker2@amd•com>, <Eric.VanTassell@amd•com>,
<vadim.fedorenko@linux•dev>, <horms@kernel•org>,
<bagasdotme@gmail•com>
Subject: Re: [PATCH V2 4/9] PCI/TPH: Implement a command line option to force No ST Mode
Date: Fri, 7 Jun 2024 17:32:50 +0100 [thread overview]
Message-ID: <20240607173250.000065d7@Huawei.com> (raw)
In-Reply-To: <20240531213841.3246055-5-wei.huang2@amd.com>
On Fri, 31 May 2024 16:38:36 -0500
Wei Huang <wei.huang2@amd•com> wrote:
> When "No ST mode" is enabled, end-point devices can generate TPH headers
> but with all steering tags treated as zero. A steering tag of zero is
> interpreted as "using the default policy" by the root complex. This is
> essential to quantify the benefit of steering tags for some given
> workloads.
This is a good explanation. Need similar in the previous patch to
justify the disable TPH entirely.
> diff --git a/drivers/pci/pcie/tph.c b/drivers/pci/pcie/tph.c
> index 5dc533b89a33..d5f7309fdf52 100644
> --- a/drivers/pci/pcie/tph.c
> +++ b/drivers/pci/pcie/tph.c
> @@ -43,6 +43,27 @@ static int tph_set_reg_field_u32(struct pci_dev *dev, u8 offset, u32 mask,
> return ret;
> }
>
> +int tph_set_dev_nostmode(struct pci_dev *dev)
> +{
> + int ret;
> +
> + /* set ST Mode Select to "No ST Mode" */
> + ret = tph_set_reg_field_u32(dev, PCI_TPH_CTRL,
> + PCI_TPH_CTRL_MODE_SEL_MASK,
> + PCI_TPH_CTRL_MODE_SEL_SHIFT,
> + PCI_TPH_NO_ST_MODE);
> + if (ret)
> + return ret;
> +
> + /* set "TPH Requester Enable" to "TPH only" */
> + ret = tph_set_reg_field_u32(dev, PCI_TPH_CTRL,
> + PCI_TPH_CTRL_REQ_EN_MASK,
> + PCI_TPH_CTRL_REQ_EN_SHIFT,
> + PCI_TPH_REQ_TPH_ONLY);
Unless these have to be two RMW operations. (if they do add a spec reference)
then this is a good example of why a field update function may not be
the right option. We probably want to RMW once.
return tph_set_reg_field_u32()
> +
> + return ret;
> +}
> +
> int pcie_tph_disable(struct pci_dev *dev)
> {
> return tph_set_reg_field_u32(dev, PCI_TPH_CTRL,
next prev parent reply other threads:[~2024-06-07 16:32 UTC|newest]
Thread overview: 28+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-05-31 21:38 [PATCH V2 0/9] PCIe TPH and cache direct injection support Wei Huang
2024-05-31 21:38 ` [PATCH V2 1/9] PCI: Introduce PCIe TPH support framework Wei Huang
2024-06-07 15:56 ` Jonathan Cameron
2024-06-07 16:27 ` Bjorn Helgaas
2024-05-31 21:38 ` [PATCH V2 2/9] PCI: Add TPH related register definition Wei Huang
2024-06-07 16:17 ` Jonathan Cameron
2024-06-10 20:00 ` Wei Huang
2024-06-07 16:42 ` Bjorn Helgaas
2024-06-10 20:04 ` Wei Huang
2024-05-31 21:38 ` [PATCH V2 3/9] PCI/TPH: Implement a command line option to disable TPH Wei Huang
2024-06-07 16:27 ` Jonathan Cameron
2024-06-07 19:59 ` Bjorn Helgaas
2024-05-31 21:38 ` [PATCH V2 4/9] PCI/TPH: Implement a command line option to force No ST Mode Wei Huang
2024-06-07 16:32 ` Jonathan Cameron [this message]
2024-06-07 17:42 ` Bjorn Helgaas
2024-05-31 21:38 ` [PATCH V2 5/9] PCI/TPH: Introduce API functions to manage steering tags Wei Huang
2024-06-06 22:30 ` kernel test robot
2024-06-07 17:29 ` Jonathan Cameron
2024-06-07 17:45 ` Bjorn Helgaas
2024-05-31 21:38 ` [PATCH V2 6/9] PCI/TPH: Retrieve steering tag from ACPI _DSM Wei Huang
2024-06-04 15:30 ` Simon Horman
2024-06-05 19:34 ` Wei Huang
2024-06-07 17:39 ` Jonathan Cameron
2024-06-07 18:43 ` Bjorn Helgaas
2024-05-31 21:38 ` [PATCH V2 7/9] PCI/TPH: Add TPH documentation Wei Huang
2024-06-07 17:43 ` Jonathan Cameron
2024-05-31 21:38 ` [PATCH V2 8/9] bnxt_en: Add TPH support in BNXT driver Wei Huang
2024-05-31 21:38 ` [PATCH V2 9/9] bnxt_en: Pass NQ ID to the FW when allocating RX/RX AGG rings Wei Huang
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